Conventionally, electro-magnetic relays include a yoke made of a plate and an iron core, having an exciting coil wound on a coil bobbin, fixedly secured to form an electro-magnet. Generally, the yoke and iron core-coil combination are secured by staking. An armature is supported through a leaf spring on the yoke such that it is arranged between the yoke and the pole piece of the electro-magnet. The leaf spring is used to restore the armature. Japanese Patent Application (OPI) No. 31537/1984 discloses an electro-magnetic relay including a stationary leaf spring with a stationary contact secured to an insulating stand, and a movable leaf spring with a movable contact is mounted through an insulating member on the armature so that it is swung back and forth together with the armature.
There is a large demand for the miniaturization of electro-magnetic relays used for input and output interfaces in electronic circuits. This demand corresponds to the demand for increased miniaturization and integration of electronic components.
As an electro-magnetic relay is miniaturized, the components such as the leaf springs must also be miniaturized, and extremely small connecting parts must be employed. Consequently, the components must be machined with a high degree of accuracy, and the assembling work must be performed with a high degree of precision. In order to increase the productivity of such a small electro-magnetic relay, to decrease the manufacturing cost, and to maintain the reliability of the product, the number of components must be minimized and the configurations of the components must be designed so that they readily can be machined and assembled.
The thickness of the conventional electro-magnetic relay is defined by the width of the yoke and the electro-magnet. The stationary leaf spring and the movable leaf spring are arranged outside of the yoke and the electro-magnet, and therefore, the internal space defined by these components is necessarily large. As a result, the ability to miniaturize the electro-magnetic relay is limited.
Efforts have been made to miniaturize the components. However, attempts to reduce the number of components, to simplify the configuration of components, and to improve the component assembling efficiency have not proven satisfactory. Indeed, as miniaturization of the components is increased, difficulties in machining and assembling the components have increased.